1. a device or substance that produces ions, especially one used to improve air quality by releasing negative ions
Usage: British spelling; American spelling is 'ionizer'; commonly used in air purifiers and humidifiers
2. in chemistry and physics, any agent or process that causes ionization
Usage: technical usage

Examples

• She bought an ioniser to help reduce dust and allergens in her bedroom.
• The air purifier includes an ioniser that releases negative ions into the room.
• Modern ionisers are often found in humidifiers and air-cleaning devices.
• The ioniser in the device helps freshen the air by creating charged particles.
• Many people use an ioniser to improve indoor air quality during winter months.